Advances in the art of photographic elements have led to a decrease in the amount of time allowed for processing to develop the image. For example, in medical X-ray films the total processing time has decreased from over 3 minutes to less than 60 seconds over the past few decades. Medical X-ray processing typically involves the sequential steps of development, fix, wash and dry. During development a latent image in the image wise exposed regions of a film is converted to elemental silver. During the fixing step the silver halide from the unexposed regions of the film is removed leaving a negative reproduction of the original image. The film is then subjected to washing to remove deleterious materials and finally the film is dried yielding a negative reproduction of the original image.
As the time allowed for processing decreases so does the residence time in each of the processing steps. The rates of development and fix must be rapid to insure that an image is obtained which is a faithful rendition of the input image. Incomplete development results in an image which is poorly resolved and incomplete fixing leads to a high background density and poor aging characteristics. Rapid washing requires rapid diffusion of liquid into the film binder and rapid diffusion of deleterious materials out of the film binder.
Particularly relevant to this invention is the decreased residence time in the dryer. With a decrease in dryer residence time either the amount of volatile material removed must be decreased or the rate of removal of the material must be increased. Decreasing the amount of volatile material is difficult since this has a deleterious effect on the washing. Therefore, the ideal film would exhibit relatively high absorption of solution but rapid drying abilities.
Rapid drying film is a necessity in modern photographic elements. The amount of total binder can be decreased yet this often creates physical quality problems as known in the art. A major task of the film binder is to safely harbor the silver halide grains and protect the grains from damage from surface abrasion, bending and the like. As the amount of total binder is decreased the physical damage resulting from such actions becomes noticeably worse and the films are deemed to be inferior.
Materials which are easily washed out of the film are routinely taught yet this leads to problems with processor fouling and the like. The material which washes out of the film most often contaminates the processing solutions and the materials can deposit on drive rollers in the processor or redeposit on subsequent sheets of film rendering them aesthetically displeasing.
There has been a long felt desire in the art for a binder which can absorb solution and dry rapidly without a large amount of washout material.